The present invention generally relates to disc-shaped recording medium reproducing apparatuses, and more particularly to a disc-shaped recording medium reproducing apparatus capable of placing and leaving a disc-shaped information recording medium in a state possible for reproduction within the reproducing apparatus when a case having a lid for accommodating the recording medium therein is inserted into and then pulled out from within the reproducing apparatus, and constructed to prevent an erroneous operation in which an attempt is made to load a disc-shaped recording medium into the reproducing apparatus in a state where a disc-shaped recording medium is already loaded within the reproducing apparatus.
Conventionally, in an apparatus for reproducing a disc-shaped recording medium (referring to video disc, PCM audio disc, and the like, and hereinafter simply referred to as a disc), there are types of apparatuses in which a disc is reproduced when the disc is loaded upon clamping and placing of the disc within the reproducing apparatus, by inserting into and then pulling out a disc case which has a lid and accommodates a disc therein, from within the reproducing apparatus. In this type of an apparatus, it becomes necessary to positively clamp the disc at an accurate position within the apparatus. However, in the conventional reproducing apparatus, the disc is clamped upon pulling out of the disc case from the reproducing apparatus, for example, and hence, suffered disadvantages in that the disc may not be clamped when the insertion and the pulling out operation of the disc case is rapidly performed, and that the disc may be pulled out from the reproducing apparatus together with the disc case.
Another example of a conventional type of a disc case comprises a rigid jacket for accommodating a disc, and a tray having a front part which is engaged by engaging means upon complete insertion of the disc case within the reproducing apparatus and an annular or ring portion fixed to the front part for encircling the outer periphery of the disc. The reproducing apparatus which operates together with this disc case, is constructed so that when this disc case is inserted within the reproducing apparatus to a predetermined position, the engaging means of the reproducing apparatus engages to and holds onto the front part of the tray. Hence, when the jacket is pulled out from within the reproducing apparatus, the disc is held by the annular portion of the tray and relatively slipped out from the jacket at the above predetermined position, and the outer peripheral edge part of the disc rests on and is supported by a supporting mechanism within the reproducing apparatus. Then, a turntable relatively rises within the inner side of the supporting mechanism, and the disc is placed onto and is unitarily rotated with the turntable, to perform the reproduction. After completion of the reproduction, when the empty jacket is inserted into the reproducing apparatus, the disc is relatively inserted into the jacket together with the annular portion of the tray, and the engagement of the engaging means is released. Accordingly, when the jacket is pulled out from the reproducing apparatus, the disc and the tray is obtained outside the reproducing apparatus together with the jacket in a state in which the disc and the tray is incased inside the jacket.
Thus, in the disc case for use with the conventional reproducing apparatus, the peripheral side surface of the disc is held by the engaged annular portion of the tray and the disc remains within the reproducing apparatus upon pulling of the jacket outside the reproducing apparatus. Accordingly, a supporting mechanism which is placed with the remaining disc thereon and supports the outer peripheral edge part of the disc, is provided in the reproducing apparatus. Hence, the turntable must be constructed so as to relatively move up-and-down within the inner side of the supporting mechanism. This means that the diameter of the turntable must be smaller than the diameter of the disc, and the outer peripheral edge part of the turntable thus makes contact with and supports the disc at the signal recording surface which is to the inner side of the outer peripheral edge part of the lower disc surface. Therefore, scratches are easily made on the signal recording surface part of the disc which is supported by the turntable, and especially when starting the rotation of the turntable, suffers a disadvantage in that scratches are more easily made in this case due to a force acting in a direction so as to rub the disc. Accordingly, when the disc is used many times, fine reproduction cannot be obtained due to the above scratches formed on the signal recording surface of the disc.
Moreover, upon reproduction, when a reproducing transducer of the reproducing apparatus moves to the position of the signal recording surface on the disc surface, the reproducing transducer must traverse over the annular portion of the tray. This traversing movement accordingly leads to a disadvantage in that the reproducing transducer moving mechanism must be designed so that the reproducing transducer does not collide with the annular portion, and the construction of the mechanism thus becomes complex.
Accordingly, in a United States patent application entitled "DISC-SHAPED RECORDING MEDIUM REPRODUCING APPARATUS" in which the assignee is the same as the assignee of the present application, a disc-shaped recording medium reproducing apparatus was proposed where the reproducing apparatus comprises a mechanism for enlarging an opening and its adjacent parts of a jacket upon loading of a disc which is incased inside the jacket, into the disc reproducing apparatus, and a mechanism for clamping which enters inside the jacket to clamp the disc incased inside the jacket, by riding over a lid plate which closes the opening of the jacket. According to this proposed reproducing apparatus, there is an advantage in that the disc does not make any unnecessary contact with the jacket and scratches are not introduced, when the jacket is pulled out from the reproducing apparatus after placing the disc inside the reproducing apparatus, or when accommodating the disc placed inside the reproducing apparatus into the empty jacket, since the opening of the jacket is in an enlarged state. Furthermore, another advantage this proposed reproducing apparatus has is in that the jacket can easily be pulled out from the reproducing apparatus after placing the disc inside the reproducing apparatus, since the disc is clamped by the clamping mechanism of the reproducing apparatus, and in addition, because the lid plate is independent from the operation in which the disc is relatively pulled out from within the jacket, the construction of the disc case becomes quite simple, enabling the disc case to be manufactured at low cost.
However, in this type of a reproducing apparatus, when a jacket (disc case) having a lid and accommodated with a disc therein is erroneously inserted forcibly into the reproducing apparatus in a state where a disc is still loaded within the reproducing apparatus, an accident is introduced in which the disc and the parts within the reproducing apparatus are damaged.
Therefore, it is highly desirable to provide preventing means for preventing a double-insertion of the disc case, in which a disc case accommodated with a disc therein is erroneously inserted into the reproducing apparatus in a state where a disc is already loaded within the reproducing apparatus.